Also several manufacturers (I know of some Samsung versions and Phillips) will position web services in first-level UX navigation making those TVs annoying to use as dumb TVs. There are even some models that will constantly nag you to connect them to the internet!
There's bunch of places between the video source and you that add their own buffers (not to mention the actual I-frame issues). Usually the most critical are encoders themselves (need to generate closed GOPs and a lot of commercial expensive hardware stuff doesn't give you enough control) and the player software on STBs (those usually have large buffers pre-set).
In the end it's rather large amount of work most IPTV (and digital cable) providers don't care about because... hey... where are you gonna go if you're unhappy with their service? :)
I presume the TV hides that by always taking the same amount of time to change stations.
On the other hand, I have an LG. It's "smart" but it starts up instantly and has no trouble with UX.
Lo and behold every few months something would happen which would make it clear that it was connected to the internet. I'd get banner ads. I'd get notices from the mothership about important updates. That sort of thing. Each time I'd discover that the wifi was back on and each time they'd have hidden how to remove it somewhere else.
Eventually I just changed my wifi password and that seemed to have done the trick.
Everything else is handled by the Internet connected Amazon Fire TV stick I plug into it. It is effectively a dumb TV and will not get infected by malware.
That's one thing that never happened to me with a (truly) dumb TV and I've only owned this one for a month. I sure hope the CPU hardware running this OS doesn't degrade as quickly as normal consumer PC hardware and I can expect it to run as quick and reliably as it does now in ten years from now (like the TV it replaced did).
http://boingboing.net/2016/11/09/a-lightbulb-worm-could-take...
I would agree odds are low of something that insidious... but it's hard to say "it'd be impossible for my TV to get hacked" when even light bulbs are getting attacked.
Although with the way I've got my house wired, HDMI over Ethernet would be more useful.